1. Technical Field
The disclosure relates to methods for manufacturing the light emitting diode chip, and particularly to a method for manufacturing the light emitting diode chip having electrodes with smooth surfaces.
2. Description of the Related Art
A conventional light emitting diode chip (LED) includes a substrate, a light emitting structure having an N-type semiconductor layer, an active layer and a P-type semiconductor layer formed on the substrate in sequence, and two electrodes (i.e., N-type and P-type electrodes) respectively connected to the N-type and P-type semiconductor layers. The two electrodes are always made of metal material and made by electroplating, evaporating or micro film deposition. Generally, an annealing process is provided after the electrodes are formed to reduce a fragility and residual stress of the metal electrodes and refine metal crystalline structures inside the metal electrodes to obtain a high quality of the electrodes.
However, metal particles inside the metal electrodes will diffuse to form rough surfaces of the electrodes when the electrodes are in a high temperature in the annealing process. Furthermore, since the ITO (indium tin oxide) layer on which the P-type electrode is formed has a rough surface in nature, the surface of the P-type electrode correspondingly is rough. A rough surface of the electrode will increase impedance between the electrodes and wires during a wire bonding process. Further, there are other disadvantages of the rough surfaces of the electrodes, such as the wires are difficult to be reliably attached on the rough surfaces of the electrodes, and a different color will be shown on the rough surfaces of the electrodes to confuse operators in a following testing process for the electrodes.
Therefore, it is desirable to provide a method for manufacturing a light emitting diode chip which can overcome the above shortcomings.